Apparatus for directing guns



2 Sheets-Sheet 1 E n. Rw

Illl

July 15, 1947. R. F. GARBARIN: Erm.

APPARATUS FOR DIRECTING GUNS Filed March l, 1943 NS, @n l .n @NN I July 15, 1947-. F. GARBARINI ETAL APPARATUS FOR DIRECTING GUNS Filed March l, 1943 2 Sheets-Sheet 2 M R www n MM m m .G 7m w65 im n u Patente-d July 15, 1947 UNITED STATES PATENT OFFICE APPARATUS FOR DIRECTING GUNS Robert F. Garbarin, Woodside, and Willis G.

Wing, West Hempstead, N. Y., assignors to Sperry Gyroscope Company, Inc., Brooklyn,

N. Y., a corporation of New York Application March 1, 1943, Serial No. 477,664

(Cl. 23S-61.5)

13 Claims. 1

The present invention relates to the art of directing gun re against a moving target, and particularly to means for, and methods of, directing guns against rapidly moving targets such as aircraft.

In view of the many factors entering into the prediction of future position of moving targets, the accuracy of gun directors depends to a large extent upon the complexity of the mechanism used.

Examples of prior directors may be found in Patent No. 2,065,303, for Apparatus for the con.. trol of gunre, issued December 22, 1936, in the names of E.W. Chafee, H. Murtagh and S. G.

Myers; copending application Serial Number 434,090, for Anti-aircnaft gun directing system, filed March 10, 1942, in the names of E. W. Chafee, C. G. Umstead, and L. C. Warner, and eopending application Serial Number 470,686, for Gun directing apparatus, filed December 30, 1942, in the names of D. J. Campbell land W. G. Wing.

These directors have been developed, primarily, for use in connection with relatively long range guns capable of protecting a comparatively large area. In order to obtain accurate predictions of the future positions of a target, these directors are of f a complex nature, and their manufacture involves considerable amounts of time andvmaterials. There is also. a certain delayI between the time a target is first sighted and the time that accurate predictions are furnished by the director for positioning guns to fire again-st the target. This delay is not. of suiicient length to curtail the effectiveness of lthe directors when used for relatively long ranges. range guns, it will readily be seen that a rapidly moving target might move out of range during the time required for these directors to supply accurateV predictions of the future position of the target.

Asis well known, gunsights, with or without comparatively simple prediction mechanisms are suiiciently accurate to direct the nre of relative short range guns.- For these short ranges, even 'high speed targets cannot move a very great dis- Mnl In the case of shorter 5 creases as the range is reduced, and the usefulness of the latter decreases as the range is in-` creased. Therefore, it maybe desirable to have a director for aiming certain intermediate range guns more laccurately than a gun sight, and yet be less complex and capable of predicting future positions more rapidly than the aforementioned directors.

Since shorter rang-e guns can only protect a very limited area, it follows that more guns will be required than in the case of long range guns. For this reason, a less complex director is desirable in order to permit the manufacture of more units with a given amount of time and materials.

This intermediate range may be said to lie between 500` yards and 5000 yards slant range, that is, the range in which the linear distance of the target from thev gun is between 500 and 5000 yards. These distances are merely illustrative of an intermediate range, and are not intended as limiting the invention.

In the solution of re control problems, the velocity and direction of flight of the target may be represented vectorially by a system of three mutually perpendicular vectors representing component velocities of the target. By multiplying each of these component velocities by the time of night of a projectile from the gun to ,fthe predicted future position of the target, We may obtain vectors representing three component-s of the movement of the target from its present position to its future position. Then, lby adding the three vectors representing the product of velocity times time of flight, we may determine the future position of the target.

It will be apparent that the time of flight is dependent upon the future position of the target. Hence the exact time of night may only be ascertained by a series of approximations in which a time of flight is calculated on the basis of a knownv position and the future position estimated for this time of flight; time of flight to this future position again calculated and a later future position determined, etc. Considerable time is required for the computing mechanism to make this series of approximations. However, an accurate time of flight is of value where accurate predictions are desired, as, for example, Whenlong range guns are used.

It will be apparent that the time of flight is a function of the linear distance from the gun to the future position of the target and the elevation of the future position ofthe target with respect to the plane of the gun` It is, of course, also necessary for this time of flieht to be corrected in accordance with the ballistics of the particular projectile used.

The effect of the elevation of the future position of the target upon the time of flight is small. For short and intermediate ranges, the factor of future elevation may be eliminated from computations of the time of flight. Furthermore, the linear distance from the gun to the future position of the target is, for intermediate and short ranges, approximately equal to the algebraic sum of the linear distance from the gun to the present position of the target and the product of the rate of change of this distance multiplied by the time of flight. From this, it may be said that the time of flight is a function of the linear distance and the rate of change of that distance.

In the present invention, a fictitious time ofV Y flight, hereinafter called the corrected time of Hight (tp) is used to obtain prediction. This corrected time of flight is Va value based on an approximate function of present slant range and slant range rate which may be multiplied by angular rates to obtain accurate prediction.

One expression for the corrected time of flight (t'p) is,

I Dat? z=- Dfi-Di wherein Dp is the linear distance from the gun to the target and D is the rate of change of that distance and tp is the time of night of a projectile from the gun to the future position of the target. This equation is intended solely as an example of one calculation of the corrected time of flight. the value fp however will be used throughout the specification to designate a corrected time of flight that will give Van accurate computation of the prediction angle when multiplied by the angular rate of the target.

From the foregoing, it may be said that the corrected time of flight is a function of slant range (De) and slant lrange rate (f3). Various functions of Do'and D may be used to obtain a desired corrected time of flight, as will hereinafter appear. Y f

One of the objects of the present invention is to provide a relatively simple director for accurately controlling the fire of guns for intermediate ranges.

Another object of the invention is to provide a director for aiming guns that will rapidly predict the future position kof the target.

A further object of the invention is to provide a prediction mechanism whichA will compute a time of ight immediatelyrfrom data supplied to the mechanism.

A further object of the invention is to provide a prediction mechanism in which a corrected time of flight is computed Vfrom the linear distance between the gun and the present position of the target and the rate of change of that distance.

A still further object of the invention is to provide a prediction mechanism for intermediate range directors which will accurately compute the future position of a target from information supplied as to the rates of change of the elevation and azimuth positions of the target and a corrected time of flight. y

Other objects and advantages of the invention will become apparent from the following description taken in connection with the accompanying drawings which show specific embodiments of the invention wherein: l Y

Fig. 1 is a space diagram showing the vector relationships used in the solution of the prediction problem,

Fig. 2 is a schematic diagram of a director embodying the invention in one form, and

Fig. 3 is a schematic diagram of a director embodying the invention in another form. Y

Fig. 3A is a schematic drawing of a director.

In order to facilitate an understanding of Fig. 1 the following are definitions of the various angular, linear and vector designations used in the present solution of the prediction problem.

To is the observed or present position of the target.

Tp is the predicted future position of the target.

tp is the time of flight of a shell or a projectile from the gun to the future position of the target. Y Y Y Y Y Y fp is a corrected time of flight based on an approximate function of present slant range and slant range rate.

Ao is the observed or present azimuth of the target relative to a point in the horizontal plane of the gun.

Ap is the predicted future azimuth of the target relative to the same point in the horizontal plane of the gun.

Ep is the observed or present elevation of the target relative to the horizontal planeV of the gun.

Ep is the predicted future elevation of the target relative to the horizontal plane of the gun. RQ is the observed or present horizontal rangeof the target, that is, the linear distance from the gun to a projection of To on the .horizontal plane. Y y

Rp vis the future horizontal range of the target, that is, the linear distance ofthe gun to the projection of Tp on the horizontal plane.

' HQ is the observed or present altitude of the target above the horizontal plane of the gun.

Hp is the predicted future altitude of the target relative to the horizontal plane of the gun.

D0 is the observed or present slant range of the target, that is, the linear distance between the target and the gun.

Dp is the future predicted slant range of the target, that is, linear distance between the future position Tp of the target and the gun.

The horizontal plane is a horizontal plane including the gun.

The vertical plane is aplane perpendicular to the horizontal plane and including the present position of the target and the gun.

The slant plane is a plane perpendicular to the vertical plane and including the gun and the present position of the target.

is the prediction angle, that is, the angle between a line including the gun and the present position of the target and a line including the gun and the future position of the target.

Es is the elevation component of the prediction angle measured in the vertical plane.

BAS is the azimuth component of the prediction angle measured in the slant plane.

AA is change in the azimuth angle measured in th'e horizontal plane.

EAS is the azimuth angular velocity of the target measured by a tracking device in the slant plane.

)JAH is the azimuth angular velocity of the target measured by a tracking device in the horizontal plane.

2E is the elevation angular velocity of the target measured by a tracking device in the vertical plane.

In Fig. 1 the point O represents a position of the gun; the plane OAB is the vertical plane through the gun; OBC is th'e horizontal plane perpendicular to the vertical plane and ODE is the slant plane through the gun and perpendicular to the vertical plane at OD dened by the line of sight. l

The target when in position To has a certain velocity (V) toward the future position Tp.

By multiplying the Velocity (V) by the time of ilight (tp) the distance between To and Tp is obtained. This distance is referred to as prediction.

The velocity V may be resolved into three components, one along the line of sight or slant range designated as the slant range rate; one in the slant plane designated as the slant plane azimuth rate; and one in the vertical plane designated as the elevation rate. It will be apparent that these three `component velocities are mutually perpendicular and may be added vectorially to determine the resultant velocity V.

Likewise, each of the components of the velocity may be multiplied by the time of flight to obtain three components of the prediction, one along the line of sight, one in the slant plane, and one in the vertical plane. These three components are represented by vectors in Fig. 1. The range component is designated Dtp; the slant plane component is designated EAsDptp and the vertical plane component is designated EEDptp.

Information containing the range rate (D) is supplied -by a range nder in the form of continuous slant range and the range prediction component (Dtp) may be readily calculated. However, it is not possible to measure the linear velocities of the target in the slant and vertical planes. In order to obtain value for the vectors, in Fig, 3, the azimuth angular velocity in the slant fplane (EAS), and the elevation velocity in the vertical plane (EE) are measured. The com puter of Fig. 2 measures the azimuth velocity in a horizontal plane (EAH) If these angular velocities are multiplied by the distance (De) that the target is from the gun; two linear component velocities of the target (EAsDo, EEDD) are obtained which are at right angles to each other and to the radius vector, De, and the component velocity (D).

If the component velocities are multiplied by the time of flight, the following linear predictions (EAsDotp, EEDptp, Dtp) are obtained. The vector addition of these give the change of position of the target. From the foregoing, it will be apparent that the three mutually perpendicular vectors representing the components of the targets movement from the present position To to the future position (Tp) are designated by EEDptp for the elevation component in the vertical plane; EAsDop for the azimuth component in the slant plane;.and Dtp for the range component. From these vectors, the azimuth and elevation predic tion angles can be obtained. In the embodiment of the invention shown in Fig. 3 the azimuth component is computed in a slant plane as just described and is then transformed into a horizontal plane for furnishing data for controlling the position of a gun in azimuth'. In Fig. 2 the angular velocity EAH of the target is measured directly in a horizontal plane and multiplied there by time of flight. Transformation of the azimuth data from slant plane to horizontal plane is not required in this case and the diagram 6 of Fig. 1 only applies generally to the embodiment of Fig. 2.

The following equations, some of which are approximations, are thought to be suicient to give an understanding of the mechanism about to be described. The equations are believed to be in such form as to give those skilled in the art an understanding of the invention and therefore details of their derivation have been omitted.

Referring to Fig. 1, it may be shown that 2ED D+1' f17 As previously explained the corrected time of flight (tp) may be computed as a function of D0 and D in accordance with the following equation:

tan AA= (4) and D0+1tp Sec micos (Ewan) 5) hence,

EASI-)atv (D+Dl) se@ 5E. @0S (lawn.)

By substituting Equation 2 in Equation 6 zAst'v sec 6E., cos (Erl-5E.)

This may be written as tan AA and since tan AA= tan AA= (7) EASt/p (l-tan Eo tan 5E.) cos Eu (s) By substituting for EAS in Equation 8 tan AAG-tan E0 tan Es) :EAHtp From Fig. 1 it may also be shown that H p=Rp tan Ep hence, by equating the values of I-Ip in Equations 11 and 12 Rp tan Ep= R0+1tp tan (Ewans 13) Since from Fig. 1

R0+Rfp=Rp cos AA 14) By substituting the va1ue of RDJVRtp in Equation 13 Rp tan EgnzRp tain (EG+ES) COS AA This may be Written as Ep: tan "1(tan` (Eo-l-Es) cos AA) (16) For a reason to be subsequently explained, the sum of E0 and Es is subtracted from both sides of Equation 16 to give By the mechanism shown in Fig. 2 it is pro`V 7 posed to 'solve Equations 2, 3, 10 and 17 to obtain values of tp, Es, AA, and AE. When these values are available, an accurate prediction of the future position of the target may be computed.

From a suitable range finding mechanism which may be of either the optical or radio type, a value of the present range (D) of the target is continuously supplied to the operator of the director. The director operator introduces this value of present range continuously into the director by means of a handwheel I on a shaft 2 which carries a pinion 3 which'meshes with a rack 4 to displace ball carriage of a variable speed drive mechansm designated generally at 6. A disc 1 of the Variable speed drive 6 is driven by a constant speed motor 8. It will be apparent that cylinder or drum 9 of the variable speed drive will be rotated at a speed proportional to the displacement of the ball carriage.

If the operator is supplied with the value of present slant range on a dial, he will turn the handwheel I until the ball carriage 5 is displaced suciently to rotate the drum Si at a speed whereby a range indicator I9 will be matched with the value appearing upon the range indicator (not shown) that is positioned by the range nder mechanism. When the indications are matched, the ball carriage-and therefore the shaft 2 both will be displaced an amount proportional to the rate of change in the slant range. A pinion I2 on the shaft 2 meshes with a rack I3 that translates a threedimensional cam designated generally at I4 in accordance with the rate of change in slant range (D).

The drum 9 drives one input of a differential I5; the other input is driven by the shaft 2. The output shaft I6 is thereby rotated an amount proportional to a present slant range (Dn) of the target at any given instant. This shaft carries an elongated pinion I1 that drives a gear I8 to rotate the cam I4. One surface I9 of the cam I4 islaid out in accordance with Equation 2 as a function of the slant range and the slant range rate. Since the cam is translated in accordance with the slant range rate and rotated by an amount proportional to the slant range, movements of a follower 2| that rides on the surface I9 will be proportional to the corrected time of flight (t'p).

Follower 2| is provided with a rack 22 that meshes With a pinion 23 to turn a shaft 24 an amount proportional to the corrected time of night (tp). The rotation of this shaft displaces a yball carriage 25 of a variable speed drive mechanism designated generally by 26 by means of a rack 21 connected to the ball carriage 25 and a pinion 28 on the shaft 24. Similarly the ball riage 39 of a variable speed drive mechanismV designated generally at 4I in accordance Vwith the rotation of the shaft 36. Displacement of the ball carriage 39 transmits motion from a 8 disc 42 that is driven by constant speed motor 43 to a drum 44 that is thereby rotated at a speed proportional to the extent of rotation of the shaft 36. One input of a differential 45 is driven by the shaft 36 and another input 46 is driven by the drum 44.

It will be apparent that the output 46 of the differential 45 will rotate at a speed proportional to the elevation angular velocity of the target in a vertical plane (2E) provided of course the telescope 34 is maintained on the target. Telescope 34 is rotated about a horizontal axis at a speed proportional to the speed of shaft 46 by means of a pinion 41 that drives a gear 48 connected to the telescope 34 by a shaft 49. y

The shaft'46 in addition to being rotatedv at a speed proportional to the elevation angular velocity (EE) of the target is also rotated by an amount proportional to the present elevation (En) of the target. A shaft 5I driven by the shaft 46 through bevel gears 52 and 53, rotates through bevel gears 54 and 55 shaft 56 at the same speed as shaft 46. This shaft 56 drives a disc 51 of the variable speed drive 26.

lSince the ball carriage 25 of the variable speed drive 26 is displaced an amount proportional to the corrected time of flight tp and the disc 51 is rotated at a speed proportional to the elevation velocity 2E of the target, the drum 58 will be rotated at a speed proportional to the product of 2E and. tp.

Drum 58 drives a shaft 59 that is connected to one of the inputs of an equating device 6I which may be of any suitable mechanical or electrical form such as a differential, an eddy current device, or4 a transformer for supplying zero output when the two input rates are matched. The other input, shaft 62 of the device 6I, is driven by a drum 63 of a variable speed drive designated generally at 64. A disc 65 of this variable speed drive is rotated by a constant speed motor 66.

The device 6I operates follow-up contacts 61 and 68 to energize a follow-up motor 69 which then rotates in one direction or another depending upon which of the input shafts of the device 6I is rotating at a greater speed. When the input shafts are rotating at equal speeds, both of the contacts 61 and 68 are open.

The follow-up motor 69, hereinafter referred to as the Es follow-up motor, drives a cylinder 1I having a cam groove 12 which moves a follower 13 an amount proportional to the tangent function of the movements of the Es followup motor. The follower 13 displaces a ball carriage 14 of variable speed drive 64. Since the disc 65 is rotated at a constant speed, the drum 63 will be rotated at a speed proportional to tan Es, provided of course the Es follow-up motor is rotated an amount proportional to the elevation component of the prediction angle (Es).

In operation, drum 58 of the variable speed drive 26 will be rotated at a speed proportional to the product of the elevation velocity of the target (2E) and the corrected time of flight (tp) This rotation will cause the device 6I to close one of the contacts 61 or 68 to drive follow-up motor 69 an amount sufficient to displace ball carriage 'I4 so drum 63 will be rotated at the same speed as drum 58. When equilibrium is reached, it will be apparent that the conditions of Equation 3 have been fulfilled and the follow-up motor will necessarily have rotated an amount proportional to the elevation component of the prediction angle (Es). Y

The follow-up motor 69 is coupled to a shaft 15 which drives one of the inputs to differential 16 referred to further on and also rotates a pinion 11 that meshes with a rack 18 to translate a cam 19. The shaft 46 operates through bevel gears 8| and 82 to drive a shaft 83 which carries an elongated pinion 84. The pinion 84 meshes with a gear 85 to rotate the cam 19.

The cam 19 is translated an amount proportional to the elevation component of the prediction angle (Es) and rotated in an amount proportional to the present elevation angle (E). The surface of the cam 19 is laid out in a manner such that follower 86 will be displaced by the cam 19 an amount proportional to (l-tan E0 tan Es). Follower 86 displaces a ball carriage 81 of a variable speed drive designated generally at 88 having a disc 89 which is driven by the constant speed motor 66. Thus drum 9| of the variable speed drive 88 is rotated at a speed proportional to the expression (1-tan E0 tan Es) A drum 9| drives shaft 92 which also rotates a disc 93 of a variable speed drive designated generally at 94 in accordance with the expression (l-tan E0 tan BES).

The azimuth operator rotates a handwheel 95 to track the target in azimuth by means of a telescope 96 in a manner similar to that described in connection with the elevation operator. Rotation of the handwheel 95 turns the shaft 91 carrying a pinion 98 which meshes with a rack 99 that is connected with ball carriage |0| of a variable speed drive designated generally at |02. The variable speed drive has a disc |03 driven by a Vconstant speed motor |04. Rotation of handwheel 95 causes displacement of the ball carriage |0| whereby drum |05 is rotated at a speed proportional to the azimuth velocity (EAH) of the target measured in the horizontal plane, since the telescope 96 is rotated about a vertical axis.

The telescope 96 is rotated to follow the target by a shaft |06 that is rotated by gear |01 which is driven by a pinion |08. Rotation of cylinder |05 rotates a shaft |09 which drives one of the inputs of a differential the other input of which is driven by the shaft 91. It will be apparent that the output shaft l2 of the differential is rotated an amount proportional to the present azimuth angle (Ao) of the target and is rotated at a speed proportional to the azimuth velocity (EAH) of the target in the horizontal plane.

Shaft ||2 acts through bevel gears ||3 and ||4 to drive a shaft ||5 that rotates disc ||6 of the variable speed drive 3|. Since the ball carriage 29 of the variable speed drive 3| is displaced an amount proportional to the corrected time of flight (t'p), drum ||1 of the variable speed drive wil1 be rotated at a speed proportional to the product of the azimuth velocity of the target in a horizontal plane and the corrected time of flight (EAHXlp).

The drum ||1 drives a shaft ||8 which forms one of the inputs of an equating device |9 similar to the device 6| previously described. The device 1 9 controls electrical contacts |2| and |22 whereby a follow-up motor |23 is energized to rotate in one direction or another depending upon which f of the input shafts of the device ||9 is rotating at a greater speed. The motor |23, hereinafter referred to as the AA follow-up motor, rotates a shaft |24 which drives a shaft |25 through bevel gears |26 and |21.

Shaft |25 rotates a cylinder |28 having a cam groove |29 that positions a follower |30 in accordance with the tangent function of the rotation of the shaft |25, that is tan AA. Follower |30 displaces a ball carriage |3| of the variable speed drive 94. Since the disc 93 of the variable speed drive 94 is rotated at a speed proportional to the expression (l-tan E0 tan Es) and the ball carriage is displaced an amount proportional to tan A-A, drum |32 of the variable speed drive is rotated at a speed proportional to the product tan AAG-tan Ea tan Es) When equilibrium is reached and both contacts |2| and |22 of the device I |9 are open, the followup motor will have rotated shaftl |24 an amount proportional to the change in the azimuth angle (AA). and the Equation 10 will be satisfied.

The AA follow-up motor |23 rotates shaft |33 which drives one of the inputs to a differential |34, an amount proportional to the angle (AA). The other input of the differential |34 is driven by a'shaft |35 that is driven through bevel gears |36 and |31 byshaft ||2 an amount proportional to the present azimuth (A0) of the target. Therefore, the differential |34 rotates a shaft |38 an amountproportional to the algebraic sum of the present azimuth angle (A0) and the change in azimuth angle (AA). Since this sum is equal to the futureazimuth angle or angle of train of the guns, the shaft |38 may position a suitable data transmitter |39. of any suitable type such as a Selsyn or Telegon thai-,transmits the angle of train data to the guns in a conventional manner.

Rotation'of shaft |24 rotates a pinion |4|. This pinion meshes with a rack |42 which translates a cam |43 in accordance with the change in azimuthangle (AA). 1 Cam 43 isrotated by a gear |44 driven by `an elongated pinion |45 that is rotated by a shaft |46. Shaft |46 is driven by the output of the differential 16, the inputs of which are driven by shafts 15 and 83. Since the rotation of these two shafts isrproportional to the elevation component of the prediction angle (BES) and the present elevation angle (E0) respectively, the output of the differential 16 will drive shaft |45 an amount proportional to the algebraic sum of these two angles. Hence, the cam |43 will be rotated an amount proportional to the sum of thesetwo angles. Y Y.

Since `the cam |43 is translated proportionally to AAand rotatedan amount proportional to (En-i-Es), the cam surface might be designed to move a camv follower an amount proportional to Ep in accordance with Equation 16. However, this would be a very large angle and would require the use of poor scale factors. Since the cam |43 is rotated in accordance with the sum of the angles (E0) and (Es), this sum may be subtracted from the surface of the cam thus providing the movement of a cam follower over the surface of a cam an 'amount proportional to Ep-(Eo-l-Es). This value is designated-AE and the cam |43 is laid out in accordance with Equation 17,

Thus, cam follower |41 is displacedan amount proportional to AE. A rack |48 connected to the cam follower |41 rotates a pinion |49 which drives a shaft |5| forming one of the inputs to a differential |52. The other input of the differential |52 is driven by the shaft |46 which is rotated an amount proportional to the sum of the angles (En) and (Es). Shaft |53 representing the output of differential |52 will thus be rotated an amount proportional to Eo-t-Es-l-AE or an amount proportional to the future elevation angle (Ep). This future elevation angle is the actual This transmitter may be;

11` elevation of the future position ofthe target. In order to supplyelevation data to the guns it is necessary to correct the elevation prediction angle for variations due to the trajectory of the projectile in the vertical plane, that is, superelevation 11).

For purposes of this director, it has been assumed that super-elevation p)jis a function of future slant range (Dp), and the angle equal to the `sum of therpresent relevationangle andthe elevation component of 'the prediction angle, namely, (E-MES).

As was stated atthe outset of the present description, future slant range (Dp), when prediction angles are small, is approximately equal to the sum, of theA present slant range (Dp)V plus the product -of the slant range rate (D) times the time'o'fliiight s (tp).VV Since the time of flight (tp) is a Yfunction of the slant range (D0) and slant range rate (D), the future range (Dp) mayv be said to be approximately equal to a function of the present slant range (Deland slant range rate (D). Based on this infomation, another Surface |54 of the @am |.4 may be laid out to displace a follower |55 an amount approximately equal to the future slant range (Dp) for given values of the present slant range (D0) and range rate (D) which translate and rotate the cam |4 respectively.

Follower |55 displaces a super-elevation (d) cam |56. The cam |56 is rotated by a gear |5'| that is driven bya pinion |58. Pinion |58 is rotated an amountproportional to (Eb-i-Es) by gearing from the shaft `|46 including pinion |59, gear |6|,.beve1 vgearsllZ and bevel gears |63 which drive 'a shaft y |64 on Vwhich the pinion |58 ismounted. It will be apparent that the lift of follower'lf Von cam|56 will be proportional to the' super-elevation, since the surface ofthe cam is designed to give this value for vgiven values of future `range (Dp), and (Ep-l-Es) which translate 'and rotate the cam |56, respectively.

Follower |65 translatesV a rack |66 which engages and rotates a pinion |61 to drive one of the inputs `of a differential |68 by means of a shaft |69. The other input ofpthe'diierential |68 is driven by the shaft |53 in raccordance with the future elevation angle (Ep) Thus, this differential` |68 algebraically adds the' future elevation (Ep) andI theV super-elevation p) to drive from its output Va shafty |'|l in accordance with the quadrant elevation to be transmitted to the guns. The `shaft positions 'a quadrant elevation transmitter |12 that may be of any well known type such as a Selsyn or fTelagon transmitter that is adaptable to transmit elevation data to the guns.

ForV comparatively small prediction angles the director described will give very accurate results although the VmechanismI is much less complex thanthe directors used for longer ranges. Also, the prediction mechanism gives an accurate solution within a very short time after the operators begin tracking a target. Y

Although simplicity hasbeen stressed in the above' description of the intermediate range directorfthe advantageous Varrangement of the various mechanisms should also be noted. For example, very little force is vrequired of the respective cam followers. With the vexception of the AE Vcam follower, these followers are used only to displace ball carriages of variable speed drive or to' displace other cams. The AE cam follower Vis used only to. drive one'input of the sFaIa-l La@ 1) and aA,=tan-1 M (2) D+Dt As was previously pointed out, a corrected time of flight of a projectile from the gun tothe future position of the target may be computed on the basis vof the following equation By substituting the value of tp in Equations 1 and V2, it will be seen that i Madan-12m', (5)

Thus, the elevation component (Es) of the prediction angle may be determined from the elevation velocity (2E) of the target and the corrected time of flight, which is a function of the present range (D0) and the range rate (D).

If we have the vvalues of the slant range (Do), slant range rate (D), elevation velocity (2E) and azimuth velocity (EAS) in the slant plane, it is possible to compute the elevation component (BES) and azimuth or lateral component (As) in the slant plane of the total prediction angle, that is the angle between the present slant range of the target and the future Slant range (Dp). Having obtained these components in the slant plane,.it is only necessary to convert them to the 'horizontal plane in order to obtain the future elevation (Ep) of the target and the future azimuth (Ap). The future azimuth (Ap) is merely the sum of the present azimuth (Ap) and the change in azimuth (AA).

The director illustrated in Fig. 3 is supplied with present slant range information continuously from a suitable range under (not shown) in a manner similar to` that described inconnection with Fig. 2. This information may be supplied in any conventional manner, as, for eX- ample, by a Vrange indicator. The operator of the'director introduces vthis slant range (De) continuously into the director by matching a range indicator |8| with the range indicator that is actuated by the range finder.

The range operator matches the indicator |8| byadjusting a handwheel 82 that rotates shaft |83 carrying apinion |84. The pinion |84 meshes with a rack |85 to translate ball carriage |86 of a Variable speed drive, designated generally as |81, the disc |88 of which is driven by a constant speedmotor |86. When the indicator |8| is continuously matched with the indicator actuated by the range finder, the ball carriage |86 will be displaced an amount proportional tothe rate of change of the slant range, and the cyl-l and 23 inder |9| of the variable speed drive |81 will be rotated at a Speed proportional to this slant range rate (D). The cylinder |9| rotates a shaft |92 which drives one input of a differential |93, the other input being driven by a shaft |94 that is rotated through bevel gears |95 and |96 by the shaft |83. The output of this differential is equal to the present slant range (D) of the target, and the shaft |83 is rotated an amount proportional to the rate of change (D) of this range.

A lead screw |91 on the shaft |83 translates a support |98 for a pair of cams |99 and 20| that are rotatably mounted in the support 98. These cams have gears 202 and 203 that mesh with pinions 204 and 205, repsectively, on a shaft 205 that is rotated by the output of the differential |93 in accordance with present range of the target. It will be apparent, therefore, that the cams |99 and 20| are translated an amount proportional to the slant range rate (D) of the target and are rotated an amount proportional to the slant range (D0) thereof.

l'lhe surface of the cam |99 is laid out in such a manner that the lift of a follower 201 riding thereon will be proportional to the corrected time of flight which, as has been previously explained, is approximately equal to a function of the slant range and slant range rate.

rEhe follower 251 translates a pair of cams 259 and 229 which are rotated in accordance with the azimuth slant plane and elevation velocities, respectively, of the target in a manner to be described.

A free gyro designated generally at 2|| is rigidly mounted on the sighting instrument (not shown) of the director which tracks the target in elevation and azimuth. One arrangement for providing azimuth and elevation movements for the sighting instrument is to mount the director casing for rotation in azimuth on a pedestal and to mount the sighting instrument on the director casing for rotation about a horizontal axis (in elevation) relative to the casing. The gyro 2|| is of conventional construction, having a rotor 2|2 pivotally mounted in a gimbal ring 2 I3 which is supported in frame 2|4 so it is free to rotate about a horizontal axis. A shaft 2 I 5 integral with the rotor of the gyro 2|| is restrained against movement about a vertical axis by a ring indicated schematically as a bail 215 for controlling movements of the gyro about this vertical axis.

In tracking the target, the operator controls movements of the sight by applying torques to the gyro through rotation of handwheels 2 I1 and 2 8 for slant azimuth and elevation, respectively. Rotation of the handwheel 2 1 acts through shaft 2|9, bevel gears 22| and 222 and compensating differential 229 to rotate shaft 223. This shaft drives through bevel gears 224 and 225 to rotate shaft 225 which applies torque to the horizontal shaft 221 of the gyro by means of a pulley 228, springs 229 and pulley 230 on the shaft 221.

Torque applied to the shaft 221 is applied to the horizontal axis of the gyro, and will cause the gyro rotor to precess about its vertical axis at a rate proportional to the torque applied. This movement of the gyro rotor about its vertical axis causes the shaft 2|5 to move the ring 2|6, thus displacing arm 23| attached thereto. The arm 23| is arranged alternatively above a pair of contacts 232 and 233, depending upon the direction in which the gyro precesses. As will subsequently appear, these contacts 232 and 233 control an azimuth motor which drives the director casing,

1.4V sight and gyro frame 2|4 in azimuth at a `rate determined by the precessicn of the gyro rotor.

Similarly, rotation of handwheel 2|8 Vapplies torque to the vertical axis of the gyro through shaft 234, bevel gears 235 and 235, compensating diiferential 240, shaft 231, pulleys 233 and 239 and springs 24|.- This torque applied to the yertical axis of the gyro causes the gyro rotor to precess about its horizontal axis at a rate proportional to the torque applied. This procession about this horizontal axis causes arm 243 to close one of the contacts 244 or 245, depending upon the direction of the movement of the gyro.

Contacts 244 and 245 control the direction of rotation of a motor 246 which rotates the sight and gyro frame 2|4 in elevation relative to the director casing by means of mechanism shown schematically in Fig. 3A of the drawings. The rate of this rotation in elevation is proportional to the elevation precession rate of the gyro, and hence iS proportional to the torque appliedby rotation of handwheel 2|9.

In tracking a target in elevation, the sighting instrument and gyro must move relative to the casing. Assuming a certain torque is applied through handwheel 2|8, the gyro rotor will precess in about its horizontal axis at a rate proportional to the torque applied. This precession causes motor 245 to move the gyro frame together with the sight relative to the director casing. Provision must be made to prevent the application of undesired torque due to this relative movement. Shafts 40| and 402, forming inputs to differentials 220 and 240, are rotated by shaft 403 from motor 245 through suitable gearing 404 and 405 in accordance with the elevation movement (E0) of Ythe gyro frame 2|4 and the sighting vinstrument. Thus, the outputs of differentials 220 and 249, namely shafts 223 and 231 rotate with the gyro frame in elevation, and rotate relative to the gyro frame only to apply torque proportilonal to the displacement at handwheels 2 I1 and 2 8.

The tracking operator, by turning the handwheels 2|1 and 2|8, causes the gyro to precess about its vertical and horizontal axes at a rate proportional to the slant azimuth and elevation velocities of the target in order to keep the sighting instrument tracking the target.

From the foregoing description, it will be seen that the angular displacement of the shaft 2|9 by handwheel 2|1 is proportional to the azimuth angular rate of the target in a slant plane (EAS), provided the sight is tracking the target. Rotation of the shaft 2|9 acts through bevel gears 25| and 252 to drive a shaft 253. Shaft 253 rotates an elongated pinion 254, which meshes with a gear 255 on the cam 208 to rotate the cam an amount proportional to the Slant azimuth velocity of the target in the slant plane (EAS). Since the cam 208 is translated by the follower 201 in accordance with the corrected time of ight (tp), and rotated in accordance with the slant azimuth velocity (EAS), it is so laid out that the lift of follower 255 riding thereon will beproportional to SAS in accordance with Equation 5.

Rotation of shaft 234 by handwheel 2|8 rotates the cam 209 in accordance with the elevation rate (En) by driving through bevel gears 251 and 258 to rotate an elongated pinion 259 that meshes with a gear 25| on the cam 209. Cam 209 iS so laid out that the lift of a follower 252 riding thereon will be proportional to the elevation component (ES) of the total prediction angle in accordance with Equation 4.

tan A, cos 6E,

The mechanism shown in Fig. 3 for translating and rotating the conversion cams to solve the above equations will now be described.

A rack 263 on the follower 262 meshes with a pinion 264 to rotate a shaft 266 an amount proportional to the elevation component (E's) of the prediction angle. This shaft 266 forms one input of an equating device 261, such as a differential, that actuates a pair of contacts 268 and 269 to control the direction o-f rotation of a follow-up motor 218. A shaft 21|, that is driven by .fthe motor 218 through Ibevel gears 212 and 213, forms the other input of the equating device. It will be apparent that rotation of the shaft 266 will cause the equating device -261 to close contacts 268 and 289 until the motor 218 drives the shaft 21| an amount proportional to the elevation component (Es) of the prediction angle.

The shaft 21| carries a lead screw 211 which, upon rotation of the shaft 21|, translates a support 218. A pair of cams 219 and 28| are rotatably mounted in the support 218.

The lift of the follower 256 rotates a pinion 282 by means of rack 283 to drive one input of anequating device 284 in accordance with the azimuth component (BAS) of the prediction angle in the slant plane. The device 284 controls follow-up contacts 285 and 286 which energize a follow-up motor 281 to drive a shaft 29| through bevel gears 288 and 289. The shaft 29| drives the other input of the equating device 284 and is thus rotated an amount proportional to the slant azimuth component (As) of the prediction angle` Rotation of shaft 29| acts through elongated pinions 293 and 294 which mesh with gears 295 and 296, respectively, to rotate the cams 219 and 28| amounts proportional to the slant azimuth component (As) of .fthe total prediction angle.

, As will be seen, the cam 219 is translated in accordance with the elevation component (Es) of the prediction angle and is rotated in accordance with the slant azimuth component (As) of the prediction angle. The surface of the cam 219 is such that the lift of a follower 38| riding thereon will be proportional to the expression (tan As cos Es) The lift of the follower 38| translates a cam 382 which is rotated in accordance with the sum of -the present elevation angle (Eo) and the elevation component (Es) of the prediction angle, that is, the expressionV (EH-Es). Rotation of the cam 382 in accordance with the sum of these two angles is accomplished in the following manner.

The shaft 21 I, which is rotated an amount proportional -to the elevation component (Es) of the 16 prediction angle, drives through bevel gears 303 and 384 to rotate a shaft 385. The shaft 385 then drives gears 386 and 381 to rotate a shaft 388 an amount proportional to Es. The shaft 388 drives one input of a, differential 389, the other input' of which is driven by a shaft 3|| that is rotated by the motor 246. As was explained above, the elevation follow-up motor 246 is driven in a direction to rotate the sighting instrument which follows the gyro in elevation. This motor is also used to drive present elevation (En) into the director by rotating shaft 3| The output of diiferential 389 rotates a shaft 3 I2 an amount proportional to the sum (Ea-l-Es) This shaft acts through elongated pinion 3|3 which meshes with gear 3 4 to rotate the cam 382 in accordance with the expression (Eo-i-Es) Since the cam 382 is translated in accordance with the expression (tan As cos E's) and is rotated in accordance with the sum (E0-HES) the surface of the cam may be designed so the lift of a follower 3|6 riding thereon will be proportional to the azimuth change (AA) in the horizontal plane in accordance with Equation '7.

A rack 3|1 on the follower 3|6 rotates a pinion 3|8 which drives a shaft 3|9 an amount proportional to the azimuth change (AA). The shaft 3| 9 drives one input of a differential 32|, the other input of which is driven by the motor 241 through shaft 322. As was previously explained, the motor 241 is driven to rotate the gyro and the sight in azimuth to follow the target. Thus, this motor rotates an amount proportional to the present azimuth (A0) of the target.

It will be apparent that the output of the differential 32| will be equal to the sum of the present azimuth (A0) and the change in azimuth (AA), which is the angle of train (A. T.) of the guns. This angle of train may be transmitted to the guns in any suitable manner, by an electric data transmission system.

Since the cam 28| is translated in accordance with the elevation component (EES) of the prediction angle and rotated in accordance with the azimuth component (As) of the prediction angle, the surface of the cam may be such that the lift of a follower 325 riding thereon will be proportional to the expression 1 1/1 -l-tan2 8A, cos2 AEs The follower 325 translates/a cam 326 that is rotated by a gear 321 which meshes with the elongated pinion 3|3. As was explained above, the pinion 3|3 is rotated an amount proportional to the sum of the present elevation (E0) and the elevation component (Es) of the total prediction angle. Hence, the cam 326 is also rotated an amount proportional to the sum (Eo-l-Es).

The surface of the cam 326 may be laid out so a follower 329 riding thereon will be displaced an amount proportional to the future elevation (Ep) of the target in accordance with Equation 7. However, the angle (Ep) is relatively large, and since the cam is rotated in accordance with (EO-i-Es), the sum of these two angles may be subtracted from the surface of the cam, whereby the follower will be displaced an amount equal t0 Ep- (Eo-I-ES).

A rack 33| on the follower 329 rotates a pinion 332 which in turn rotates a shaft 333. The shaft 333 drives one input of a differential 334 an amount proportional to Eli-(Eo-l-Es). The other input of the differential 334 is driven by a shaft 335 that is rotated through bevel gears 336 and 331 by the shaft 3|2. Since the shaft 3|2 is rotated in accordance with (Ep-l-Es), the differential will add this sum to the rotation of shaft 333, whereby the output of the differential 334 will rotate a shaft 338 an amount proportional to the future elevation (Ep). The shaft 338 actuates a follow-up switch 33S to close conta-cts 34| and 342 to control the direction cf rotation of a follow-up motor 333. The motor 3&3 acts through gears 3M and 335 to drive a shaft 3115 an amount equal to the shaft 338, which is pro-- portional to the future elevation (Ep).

In order to obtain the elevation angle to be transmitted to the guns, it is necessary to add a correction for super-elevation due to variations in the trajectory of the projectile in a vertical plane. The Ep follow-up motor 333 drives through the shaft 346, bevel gears 331 and 348, shaft 349, bevel gears 353 and 35| to rotate a shaft 352 andan elongated pinion 353 an amount proportional to the future elevation (Ep). Pinion 353 meshes with a gear 354 to rotate a cam 355 that is translated in accordance with the movements of a follower 350 on the cam 20|.

Since for small prediction angles the future range (Dp) is approximately equal to the slant range (Dp) plus the slant range rate (D) times the time of flight (tp), the future slant range is approximately equal to a function of the slant range (Dp) and slant range rate (D). Since the cam 20| is rotated in accordance with the slant range (Dp) and is translated in accordance with the slant range rate (D), the surface of the cam may be laid out so the follower 356 riding thereon will be displaced an amount approximately proportional to the future range (Dp).

Since super-elevation varies in accordance with the future elevation (Ep) and the future range (Dp), the surface of the cam 355 is such that a follower 358 riding thereon is displaced an amount proportional to the super-elevation. A rack 359 carried by the follower 358 rotates a pinion 36| which drives a shaft 362 forming one of the inputs of a differential 363. The other input of the differential 353 is driven by the shaft 349 in accordance with the future elevation (Ep). It will be apparent that the output of the differential 363 will be the sum of the future elevation (Ep) and the super-elevation, which is the quadrant elevation (Q. E.). Quadrant elevation may be transmitted by a suitable data transmission system to control the position of the guns.

Equations 4 and 5 determine the elevation and azimuth components (Ep and As) of the prediction angle in accordance with the tangent function of these component angles. It has been found that the other functions may be substituted for these tangent functions to obtain the components of the prediction angle in a similar manner. When other functions of the component angle are used, it is also necessary to use other functions of slant range and slant range rate to ascertain a corrected time of flight that will give accurate prediction. For example, accurate predictions may be obtained by substituting sine functions for the tangent function of Equations 4 and 5.

Thus, the elevation component (Es) of the prediction angle may be said to be a function of the slant range, slant range rate, and elevation velocity of the target. Similarly, the azimuth component (As) of the prediction angle may be determined as a function of the slant range (D),

slant range rate (D), and azimuth Velocity (Eps).

It will be apparent that the same quantities would be used as known values, that is, inputs to the predictor, and that similar values of the components would be obtained merely by substituting different cams in the mechanism corresponding to the functions used.

The prediction problem may also be approached empirically instead of mathematically. If a target is assumed to have a certain orientation, direction and velocity, its future position may be accurately calculated. Knowing the present position and the correct future position, it is possible to calculate the prediction angle. It is also possible to calculate the value of the function of slant range and slant range rate, that is, f(Dp, D) that could be combined with a function of the prediction angle to give an accurate prediction.

By selecting different values for the orientation, direction, and velocity of the target, the varying prediction angle and the varying Values of f(Dp, D) may be tabulated. After making this tabulation, cams similar to cams |93, 208, and 209 may be designed to give accurate prediction.

Thus, it may be said that a function (F) of the prediction angle components (Es) and (As) would equal a function (f) of slant range (Dp) and slant range rate (D) multiplied by the target velocity. This may be expressed in the following manner:

F(A5)=f(D0, D)2As (8) and FoAo :fung 15o sp 9) These equations are similar to Equations 1 and 2, except that different functions of the components of the prediction angle are used and also the corrected time of flight is a different function of the slant range and slant range rate. Any functions may be used in these equations to 0btain predictions and the function best suited for the purpose desired may be determined from tabulations of the results obtained.

In both of the intermediate range directors described, angular rates are used to obtain accurate predictions. These mechanisms are not Subj ect to the error normally inherent in solutions based upon angular rate multiplied by time predictions. This error is eliminated by computing a corrected time of flight (t'p) as a function of slant range (D0) and slant range rate (D). Intermediate range directors embodying the present invention provide accurate predictions within the range limits for which they are designed and at the same time are much less complex than the long range directors.

In addition, prediction of future position is transmitted by the director to the guns almost immediately after the director operator begins tracking the target. As has been stated, it is essential for intermediate range operations, that the interval between sighting the target and obtaining accurate prediction be comparatively short.

As many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A director for controlling the lire of guns against moving targets comprising means for setting into said director azimuth and elevation velocities of a target, a second means for setting into said director the range and the rate of change of said range, a third means actuated by said second means for computing time of ight as a function of said range and the rate of change of saidirange, a prediction mechanism actuated by the first mentioned means and said third means for multiplying respectively said azimuth and elevation velocities by said time of flight to obtain azimuth and elevation components of the predicted change in the position of said target, and another means responsive to the actuation of said prediction mechanism for converting said components into changes in gun aiming angles.

2. A director for controlling the nre of guns against moving targets comprising, a first device for setting into said director the azimuth and azimuth velocity of a target, a second device for setting into said director the elevation and elevation velocity of said target, a third device for setting into said mechanism the range of said target and the rate of change of said range, means actuated by said third device for instantaneously computing time of night solely as a function of said range and said range rate, a predictor mechanism actuated by said first and second devices and said means for multiplying said azimuth and elevation velocities respectively by said time of flight to obtain azimuth and elevation prediction angles, means responsive to the actuation of said ,prediction mechanism for converting said prediction angles into changes in gun aiming angles, and means responsive to the actuation of said first and second devices and said last-named means for adding respectively said changes in gun aiming angles to the position of the target in azimuth and elevation to obtain gun aiming angles.

3. A director for controlling the re of guns against moving targets comprising, a tracking member for following the movements of said target, a rst device responsive to the movements of said member for setting into said director the azimuth and azimuth velocity of artarget, a second device responsive to the movements of said member -for setting into said director the elevation and elevation velocity of said target, a third device for setting into said target the range of said target and the rate of change of said range, means actuated by the third device for computing time of flight solely as a function of said range and said range rate, a mechanism in the director actuated by said rst device and said means for computing in accordance with the azimuth velocity and said time of flight an azimuth prediction angle, a further mechanism in the director actuated by said second device and said means for computing in accordance with said elevation velocity and said corrected time of ight an elevation prediction angle, and means controlled by the respective mechanisms for converting said prediction angles into azimuth and elevation changes in gun aiming angles.

4. A predictor for determining the future position of a target, comprising a first device for introducing present azimuth (Ao) and azimuth rate (ZAK), a second device for introducing present elevation (E) and elevation rate (2E), a third device for introducing .present range (D0) and range rate (D), means actuated by said third device for computing a corrected time of flight (t'p) as a function of said range and range rate, a rst mechanism responsive to said second device and said means for determining the eleva- 2o tion component (Es) of the prediction angle in accordance with the equation a second mechanism responsive to said rst and second devices and said first mechanism for determining the change in azimuth (AA) of said target in accordance with the equation tan AA(l-tan E0 tan Es) :EAHtp and a third mechanism responsive to said first and second mechanisms and said second device for determining the future elevation (Ep) of said target in accordance with the equation 5. VA predictor for determining the future position of a target, comprising a first device for introducing present azimuth (AQ) and azimuth rate (EAR), a second device for introducing present elevation (E0) and elevation rate (EE), a third device for introducing present range (D0) and range rate (D), means actuated by said third device for computing a corrected time of flight (tp) as a function of said range and range rate, a rst mechanism responsive to said second device and said means for determining the elevation component (Es) of the prediction angle in accordance with the equation a second mechanism responsive to said first and second devices and said first mechanism for determining the change in azimuth (AA) of said target in accordance with the equation tan AA(1-tan E0 tan Es)=2AHtp a third mechanism responsive to said rst and second mechanisms and said second device for determining the future elevation (Ep) of said target in accordance with the equation and means responsive to said first device and said third mechanism for compensating said `future elevation for superelevation in accordance with approximate future range and said future elevation.

6. A predictor for determining the future position of a moving target, comprising means for introducing the azimuth velocity (EAS) in a slant plane and elevation velocity (2E) of a target, a second means for introducing the range (D0) and a range rate (D) of said target, means controlled by said second means for computing a corrected time of ight (tp) as a function of said range and range rate, and a mechanism jointly actuated by the first-mentioned means and the last-mentioned means for computing the azimuth component (AS) of the prediction angle in accordance with the equation and the elevation component (Es) of the prediction angle in accordance with the equation 7. A predictor for determining the future position of a moving target, comprising means for introducing the azimuth velocity (EAS) in a slant plane and elevation velocity (2E) of a target, a second means for introducing the range (D0) and a range rate (D) of said target, means controlled by said second means for computing a corrected time of night (t'p) as a function of said 21 range and range rate, a mechanism actuated b the first-mentioned means and the last-mentioned means for computing the azimuth component (AS) of the prediction angle in accordance with the equation and the elevation component (Es) of the prediction angle in accordance with the equation anism jointly actuated by the first-mentioned f means and the last-mentioned means for computing the azimuth component (As) of the prediction angle in accordance With the equation and the elevation component (Es) of the prediction angle in accordance with the equation Esr-tan-lEEt'p another means actuated by said mechanism for converting said prediction angles to gun-aiming angles, a-nd further means actuated by the first mentioned and second means for compensating said gun-aiming angles for super-elevation in accordance with approximate future range and fui ture elevation.

9. An apparatus for computing time of flight of a projectile solely from slant range comprising a shaft displaced according to slant range, another shaft displaced according to the rate of change of slant range, a three-dimensional cam adapted to be rotated by one of said shafts and translated by the other of said shafts a lift pin for the cam, the cam being laid out empirically to displace its lift pin in accordance With the time of night for a given projectile for any combination of the displacement of said shafts.

10. An apparatus for computing time of flight solely from slant range comprising means displaced in accordance with slant range, means displaced in accordance with the rate of change of slant range, means actuated jointly by both of said means in accordance with their displacements for computing time of night empirically for a given projectile for any combination of the displacements of the iirst two means.

11. A predictor for determining the future position of a moving target including means for 0btaining the angular rates of movement of the target in azimuth and elevation, a device for obtaining the range of said target and the rate of change of said range, means controlled solely by said device for computing the time of flight of a projectile as a function of said range and said range rate, and computing means actuated jointly by both means for obtaining predicted changes in the position of said target.

12. A predictor for determining the future position of a moving target including means for obtaining the angular rates of movement of the target in azimuth and elevation, a device for obtaining the range of said target and the rate of change of said range, means controlled solely by said device for computing the time of flight of a projectile as a function of said range and said range rate, and computing means jointly actuated by the rst mentioned means in accordance with the respective angular rates of movement of the target in azimuth and elevation and by the second mentioned means in accordance with the time of flight for obtaining respectively the predicted changes in position of said target in azimuth and in elevation.

13. A predictor for determining the future position of a moving target including means for obtaining the angular rates of movement of the target in azimuth and elevation, a device for obtaining the range of said target and the rate of change of said range, means controlled solely by the device for computing the time of night of a projectile as a function of said range and said range rate, and a computer including multiplying means jointly actuated by both of said means for obtaining predicted changes in the position of said target.

ROBERT F. GARBARINI. WILLIS G. WING.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,004,067 Watson June 4, 1935 2,065,303 Chafee et al Dec. 22, 1936 2,105,985 Papello Jan. 18, 1938 1,849,611 Bussei Mar. 15, 1932 1,940,681 Henderson Dec. 26, 1933 1,999,368 Myers et al Apr. 30, 1935 

